Is this for like an RTS or some other type of game that maybe doesn’t need default character movement?
You may still be better off just using Character. Unreal is supposedly able to handle a large amount of characters pretty well.
When characters move using AI, it uses a different Movement mode, something like Navmesh_Following, instead of Ground. It might be making use of some optimizations there. Chances are whatever Unreal does is a way better optimization than what you may be attempting since it’s been worked on for so long, and people have needed large amounts of characters in the past.